1. Field of the Invention
The present invention relates to earth anchors and more particularly, but not by way of limitation, to an earth anchor having extendable anchor arms and a metal skirt attached to the anchor arms which is particularly suited to anchoring objects in soft earth, swamp or marshlands.
2. History of the Prior Art
There have been many innovations in the development of earth anchors for supporting guy wires, anchoring mobile homes and the like. Many of these developments include anchors which have extendable arms and after insertion into an anchoring hole, these arms are extended into the surrounding earth to perform the anchoring function.
However, the prior art anchoring devices have not been totally successful for use in soft earth such as sand and around streams, rivers, lakes and oceans or in swamp or marshlands.
In the construction of pipelines across swamps and the like, the pipelines have been anchored by the sinking of large concrete weights having attachment cables for connecting the pipeline thereto. This method has the obvious disadvantage of requiring large swamp barges for the handling of the concrete blocks. The gradual sinking of these blocks due to their weight and the cost of the blocks and handling thereof cause the cost of laying such pipelines to be extremely high.
One of the primary reasons for the failure of earth anchors in such applications is that in order to make the anchor arms retract into a package small enough to be inserted into a small drilled hole, the anchor arms must be rather narrow. Once these narrow anchor arms are extended into the earth, they simply do not have sufficient cross-sectional area to provide the necessary holding power.
Further, in the use of retractable or extendable anchor arms, there has been a constant danger of the locking mechanism which holds the anchor arms into an extended position, becoming loose and thereby allowing the arms to inadvertently retract and loose their anchoring power.
There have been various screw-type activated anchors such as taught in the patent to Cole et al, U.S. Pat. No. 1,606,147, issued Nov. 9, 1926 for an "Earth Anchor Device" and the patent to Handel, U.S. Pat. No. 2,217,271, issued Oct. 8, 1940 for "Expansible Earth Anchor". However, these anchors have an inherent disadvantage in that the threaded rod used for expanding the anchor after expansion, is subject to exposure to the elements and becomes rusty or corroded. Since the threaded rod is often the mechanism which locks the arms in the extended position, corrosion will destroy the locking feature in a relatively short period of time.
A further disadvantage of the subject patent is the limitation on the surface area caused by the shape and size of the anchor arms in conjunction with the hole size into which they are to be inserted.